3D Iso-surface Mesh Extractor

Write a compact, efficient C# 4.0 class that convert 3D scalar field into 3D triangle mesh, by extracting iso-surface. Input is set of PNG files, and output is binary STL file. The output mesh must represent a proper 3D solid geometry without any degeneracy (it must be watertight). The program must be compact; it must not use any third party library (other than standard .NET), use native code, nor invoke other programs. I expect a few hunderds ~ a few thousands lines of code.